Safety fuse and method of manufacturing the same



March 12, 1929. J. FRITZSCHE 1,705,360

SAFETY FUSE AND METHQD OF MANUFACTURING THE SAME med Eflc. 2a. 1926 l/IVETYTOR Jam/111:5 FRI'IZJCl/E 5 4278 flTTOR/YL'VS Patented Mar. 12, 1929.

' JOHANNES rzarrzscnn, on wrnnmt nEUs'rAnr, aos'mm SAFETY FUSE AND METHOD OF MANUFACTURING THE SAME.

Application filed December 23, 1926, Serial No. 156,690, and in Austria October 7, 1924.

My invention relates to safety fuses and the method of manufacturing the same.

Safety fuses for blasting purposes as here: tofore manufactured consist of a core and a filament covering for such core, a wrapper and a sheath surrounding such wrapper being interposed if desired between the core and the filament covering.

In the safety fuses heretofore manufactured the core consists of ordinary gun powder which is a composition containing about 10% by weight of sulphur, 14% by weight of charcoal and 7 6% of saltpeter or nitrate of potassium, the constitutents being finely powdered and intimately mixed, then moistened, pressed, dried, and granulated. Finally the grains may. be coated with graphite. Thus the powder comprising the core is a homogeneous mass of grains, each grain being like every other grain, but each grain being composed of an intimate mixture of all of the elements and compounds which constitute the powder. I

Safety fuses as heretofore manufactured with such gun powder cores are however open to a series of objections.

First of all the feed of the gun powder to the narrow nozzle through which it has to pass to form the core meets with difficulties resulting in irregularities of the core. In some parts of the core the gun powder grains are only in loose contact with each other and in others they are tightly compressed, so that the core does not burn regularly whereby the reliability of the safetyfuses as heretofore manufactured is greatly impaired. F urthermore the manufacture is dangercous as explosive gun powder has 7 to be dealt with throughout.

The object of my invention is to provide a safety fuse and a method of manufacturing the same whereby the aforesaid objections are obviated.

With this object in view my invention consists in promoting the feed of the granular core mass, consisting of discrete grains of any definite size, howevee'small, to and through the nozzle by properly agitating the coremass on its way from the container to the nozzle and through. the nozzle attached to such container. Thereby I am also enabled to use a granular core mass composed of a uniform heterogeneous mixture of discrete grains, the agitation preventing any dist-urbauce of the uniformity of the mixture.

For facilitating the understanding of-my invention I have illustrated in the annexed drawing by way of example a few ways of carrying it into practice. I wish it, however, to be understood that the mechanisms shown in the drawing do not form part of my invention.

Figs. 1, 2 and 3 are diagrammatical sections of mechanisms for carrying into practice my invention. 1 is the container for the core mass composed of discrete grains and 2 is the nozzle attached to such container. 3, Fig. 1, is a thread or wire passing through the granular core mass in the container and through the nozzle along with the core mass flowing through the nozzle, thus serving to feed the core mass through the nozzle. In order to agitate the core mass in the vicinity of the nozzle and thereby to secure a perfect uniformity of the core mass escaping from the nozzle I impart to the thread or Wire an additional, for instance, a reciprocating movement perpendicular to theaxis of the nozzle either by impartingto such thread or wire a to and fro movement by means of a cam 4 acting on the guide 5 of the thread or wire, or by rotating the guide 5 around an axis excentric thereto and coinciding with the axis of-the nozzle so, that the thread or wire moves between the extreme positions indicated in full and dotted lines in Fig. 1. In-

some cases instead of an additional movement I may provide the thread or wire with knots 6 for breaking any bridges formed bv the core mass in the nozzle or in its vicinity. The movement of the thread or wire agitates the granular core mass whereby its feed through the nozzle is promoted and any choking of the nozzle is prevented.

In Fig. 2 I have substituted for the thread or wire 3 shown in Fig. 1 a paper strip 7, passing through the container and the nozzle, such strip forming a. wrapper for the core mass in the safety fuse. As the strip moves towards the nozzle it feeds the core mass thereto and in order to agitate the core mass in the container so as to promote such feed Iprovide in the container near the nozzle rotary agitators 8, tending to facilitate the feed of the core mass towards the nozzle.

In Fig. 3 I dispense with the thread or wire 3 and with the strip 7 and the agitators 8 and provide in the nozzle 2' a helically wound wire 9. which is rotated in any suitable way so as to act as a feed screw for the core mass and agitate the latter at thesame time.

- I do not limit myself to the precise'methods way. This, however, does not form part of the present invention.

By thus agitating the granular core mass and promoting the feed through the nozzle I am enabled to use a core mass differently constituted from that heretofore employed in safety fuses. Although the core mass heretofore used has been composed of like grains each grain contained all of the elements or compounds required to constitute the powder of which the core is formed. Where my invention is employed it is possible to use discrete grains, each grain being composed, for example, of but a single ingredient entering into the composition of the core mass. For

instance I may use a mixture of grains of charcoal and saltpeter with or without the addition of sulphur. The grains of different nature may either be mixed before filling them into the container or they may be supplied separately to the container, the agitation of the grains hereinbefore referred to securing an intimate mixing of the difierent grains before or'while they pass through the nozzle. I thereby secure various advantages, as for instance with grams each of wh1ch 1s composed of but a single ingredient of the core mass. 1 may select the proportions of the ingredients as circumstances may require, for

instance discrete heterogeneous grams of gun powder of different kinds and grades. Furthermore I prefer to enclose thecore mass in:

through the. nozzle.

a wrapper or in a wrapper and a sheath of paper or similar materiallittle pervious to gases, whereby accidental escape of sparks or flames from the safety fuse is prevented and at the same time the pressure within the burning safety fuse is increased to an extent sufficient for causing the flame at the end of the safety fuse connected to the cartridge or detonator' to be projected so vigorously that the ignition of the cartridge is effected with certainty. Moreover the wrapper has for its effect that the safety fuse having a core mass-consisting of discrete grains none of which contains all of the ingredients of the core mass burns better. Finally if a core mass consisting of discrete grains is used, each grain comprising a single ingredient of the core mass, the danger of explosion before the manufacture of the safety fuses is entirely obviated, as the ingredients may be kept on store without danger and manipulated separately up to the moment when they are charged into the container.

What I claim is:

1. A method of manufacturing safety fuses comprising feeding a core composed of dis crete grains to a nozzle agitating the core mass in proximity to and within the nozzle to promote its movement through the nozzle, and surrounding the mass with a. wrapper of thin flexible material as it passes through the nozzle.

2. A method of manufacturing safety fuses comprising mixing in desired proportion discrete homogeneous grains, into a heterogeneous mass feeding the mass to a nozzle agitating the mass in proximity to the nozzle, thus promoting the movement of the mass through the nozzle, and surrounding the mass with a wrapper of thin flexible material as it passes In testimony whereof I have aflixed my signature.

' JOHANN FRITZSOHE. 

